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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * fs/libfs.c
4 * Library for filesystems writers.
5 */
6
7#include <linux/blkdev.h>
8#include <linux/export.h>
9#include <linux/pagemap.h>
10#include <linux/slab.h>
11#include <linux/cred.h>
12#include <linux/mount.h>
13#include <linux/vfs.h>
14#include <linux/quotaops.h>
15#include <linux/mutex.h>
16#include <linux/namei.h>
17#include <linux/exportfs.h>
18#include <linux/writeback.h>
19#include <linux/buffer_head.h> /* sync_mapping_buffers */
20#include <linux/fs_context.h>
21#include <linux/pseudo_fs.h>
22#include <linux/fsnotify.h>
23
24#include <linux/uaccess.h>
25
26#include "internal.h"
27
28int simple_getattr(const struct path *path, struct kstat *stat,
29 u32 request_mask, unsigned int query_flags)
30{
31 struct inode *inode = d_inode(path->dentry);
32 generic_fillattr(inode, stat);
33 stat->blocks = inode->i_mapping->nrpages << (PAGE_SHIFT - 9);
34 return 0;
35}
36EXPORT_SYMBOL(simple_getattr);
37
38int simple_statfs(struct dentry *dentry, struct kstatfs *buf)
39{
40 buf->f_type = dentry->d_sb->s_magic;
41 buf->f_bsize = PAGE_SIZE;
42 buf->f_namelen = NAME_MAX;
43 return 0;
44}
45EXPORT_SYMBOL(simple_statfs);
46
47/*
48 * Retaining negative dentries for an in-memory filesystem just wastes
49 * memory and lookup time: arrange for them to be deleted immediately.
50 */
51int always_delete_dentry(const struct dentry *dentry)
52{
53 return 1;
54}
55EXPORT_SYMBOL(always_delete_dentry);
56
57const struct dentry_operations simple_dentry_operations = {
58 .d_delete = always_delete_dentry,
59};
60EXPORT_SYMBOL(simple_dentry_operations);
61
62/*
63 * Lookup the data. This is trivial - if the dentry didn't already
64 * exist, we know it is negative. Set d_op to delete negative dentries.
65 */
66struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
67{
68 if (dentry->d_name.len > NAME_MAX)
69 return ERR_PTR(-ENAMETOOLONG);
70 if (!dentry->d_sb->s_d_op)
71 d_set_d_op(dentry, &simple_dentry_operations);
72 d_add(dentry, NULL);
73 return NULL;
74}
75EXPORT_SYMBOL(simple_lookup);
76
77int dcache_dir_open(struct inode *inode, struct file *file)
78{
79 file->private_data = d_alloc_cursor(file->f_path.dentry);
80
81 return file->private_data ? 0 : -ENOMEM;
82}
83EXPORT_SYMBOL(dcache_dir_open);
84
85int dcache_dir_close(struct inode *inode, struct file *file)
86{
87 dput(file->private_data);
88 return 0;
89}
90EXPORT_SYMBOL(dcache_dir_close);
91
92/* parent is locked at least shared */
93/*
94 * Returns an element of siblings' list.
95 * We are looking for <count>th positive after <p>; if
96 * found, dentry is grabbed and returned to caller.
97 * If no such element exists, NULL is returned.
98 */
99static struct dentry *scan_positives(struct dentry *cursor,
100 struct list_head *p,
101 loff_t count,
102 struct dentry *last)
103{
104 struct dentry *dentry = cursor->d_parent, *found = NULL;
105
106 spin_lock(&dentry->d_lock);
107 while ((p = p->next) != &dentry->d_subdirs) {
108 struct dentry *d = list_entry(p, struct dentry, d_child);
109 // we must at least skip cursors, to avoid livelocks
110 if (d->d_flags & DCACHE_DENTRY_CURSOR)
111 continue;
112 if (simple_positive(d) && !--count) {
113 spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
114 if (simple_positive(d))
115 found = dget_dlock(d);
116 spin_unlock(&d->d_lock);
117 if (likely(found))
118 break;
119 count = 1;
120 }
121 if (need_resched()) {
122 list_move(&cursor->d_child, p);
123 p = &cursor->d_child;
124 spin_unlock(&dentry->d_lock);
125 cond_resched();
126 spin_lock(&dentry->d_lock);
127 }
128 }
129 spin_unlock(&dentry->d_lock);
130 dput(last);
131 return found;
132}
133
134loff_t dcache_dir_lseek(struct file *file, loff_t offset, int whence)
135{
136 struct dentry *dentry = file->f_path.dentry;
137 switch (whence) {
138 case 1:
139 offset += file->f_pos;
140 fallthrough;
141 case 0:
142 if (offset >= 0)
143 break;
144 fallthrough;
145 default:
146 return -EINVAL;
147 }
148 if (offset != file->f_pos) {
149 struct dentry *cursor = file->private_data;
150 struct dentry *to = NULL;
151
152 inode_lock_shared(dentry->d_inode);
153
154 if (offset > 2)
155 to = scan_positives(cursor, &dentry->d_subdirs,
156 offset - 2, NULL);
157 spin_lock(&dentry->d_lock);
158 if (to)
159 list_move(&cursor->d_child, &to->d_child);
160 else
161 list_del_init(&cursor->d_child);
162 spin_unlock(&dentry->d_lock);
163 dput(to);
164
165 file->f_pos = offset;
166
167 inode_unlock_shared(dentry->d_inode);
168 }
169 return offset;
170}
171EXPORT_SYMBOL(dcache_dir_lseek);
172
173/* Relationship between i_mode and the DT_xxx types */
174static inline unsigned char dt_type(struct inode *inode)
175{
176 return (inode->i_mode >> 12) & 15;
177}
178
179/*
180 * Directory is locked and all positive dentries in it are safe, since
181 * for ramfs-type trees they can't go away without unlink() or rmdir(),
182 * both impossible due to the lock on directory.
183 */
184
185int dcache_readdir(struct file *file, struct dir_context *ctx)
186{
187 struct dentry *dentry = file->f_path.dentry;
188 struct dentry *cursor = file->private_data;
189 struct list_head *anchor = &dentry->d_subdirs;
190 struct dentry *next = NULL;
191 struct list_head *p;
192
193 if (!dir_emit_dots(file, ctx))
194 return 0;
195
196 if (ctx->pos == 2)
197 p = anchor;
198 else if (!list_empty(&cursor->d_child))
199 p = &cursor->d_child;
200 else
201 return 0;
202
203 while ((next = scan_positives(cursor, p, 1, next)) != NULL) {
204 if (!dir_emit(ctx, next->d_name.name, next->d_name.len,
205 d_inode(next)->i_ino, dt_type(d_inode(next))))
206 break;
207 ctx->pos++;
208 p = &next->d_child;
209 }
210 spin_lock(&dentry->d_lock);
211 if (next)
212 list_move_tail(&cursor->d_child, &next->d_child);
213 else
214 list_del_init(&cursor->d_child);
215 spin_unlock(&dentry->d_lock);
216 dput(next);
217
218 return 0;
219}
220EXPORT_SYMBOL(dcache_readdir);
221
222ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
223{
224 return -EISDIR;
225}
226EXPORT_SYMBOL(generic_read_dir);
227
228const struct file_operations simple_dir_operations = {
229 .open = dcache_dir_open,
230 .release = dcache_dir_close,
231 .llseek = dcache_dir_lseek,
232 .read = generic_read_dir,
233 .iterate_shared = dcache_readdir,
234 .fsync = noop_fsync,
235};
236EXPORT_SYMBOL(simple_dir_operations);
237
238const struct inode_operations simple_dir_inode_operations = {
239 .lookup = simple_lookup,
240};
241EXPORT_SYMBOL(simple_dir_inode_operations);
242
243static struct dentry *find_next_child(struct dentry *parent, struct dentry *prev)
244{
245 struct dentry *child = NULL;
246 struct list_head *p = prev ? &prev->d_child : &parent->d_subdirs;
247
248 spin_lock(&parent->d_lock);
249 while ((p = p->next) != &parent->d_subdirs) {
250 struct dentry *d = container_of(p, struct dentry, d_child);
251 if (simple_positive(d)) {
252 spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
253 if (simple_positive(d))
254 child = dget_dlock(d);
255 spin_unlock(&d->d_lock);
256 if (likely(child))
257 break;
258 }
259 }
260 spin_unlock(&parent->d_lock);
261 dput(prev);
262 return child;
263}
264
265void simple_recursive_removal(struct dentry *dentry,
266 void (*callback)(struct dentry *))
267{
268 struct dentry *this = dget(dentry);
269 while (true) {
270 struct dentry *victim = NULL, *child;
271 struct inode *inode = this->d_inode;
272
273 inode_lock(inode);
274 if (d_is_dir(this))
275 inode->i_flags |= S_DEAD;
276 while ((child = find_next_child(this, victim)) == NULL) {
277 // kill and ascend
278 // update metadata while it's still locked
279 inode->i_ctime = current_time(inode);
280 clear_nlink(inode);
281 inode_unlock(inode);
282 victim = this;
283 this = this->d_parent;
284 inode = this->d_inode;
285 inode_lock(inode);
286 if (simple_positive(victim)) {
287 d_invalidate(victim); // avoid lost mounts
288 if (d_is_dir(victim))
289 fsnotify_rmdir(inode, victim);
290 else
291 fsnotify_unlink(inode, victim);
292 if (callback)
293 callback(victim);
294 dput(victim); // unpin it
295 }
296 if (victim == dentry) {
297 inode->i_ctime = inode->i_mtime =
298 current_time(inode);
299 if (d_is_dir(dentry))
300 drop_nlink(inode);
301 inode_unlock(inode);
302 dput(dentry);
303 return;
304 }
305 }
306 inode_unlock(inode);
307 this = child;
308 }
309}
310EXPORT_SYMBOL(simple_recursive_removal);
311
312static const struct super_operations simple_super_operations = {
313 .statfs = simple_statfs,
314};
315
316static int pseudo_fs_fill_super(struct super_block *s, struct fs_context *fc)
317{
318 struct pseudo_fs_context *ctx = fc->fs_private;
319 struct inode *root;
320
321 s->s_maxbytes = MAX_LFS_FILESIZE;
322 s->s_blocksize = PAGE_SIZE;
323 s->s_blocksize_bits = PAGE_SHIFT;
324 s->s_magic = ctx->magic;
325 s->s_op = ctx->ops ?: &simple_super_operations;
326 s->s_xattr = ctx->xattr;
327 s->s_time_gran = 1;
328 root = new_inode(s);
329 if (!root)
330 return -ENOMEM;
331
332 /*
333 * since this is the first inode, make it number 1. New inodes created
334 * after this must take care not to collide with it (by passing
335 * max_reserved of 1 to iunique).
336 */
337 root->i_ino = 1;
338 root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
339 root->i_atime = root->i_mtime = root->i_ctime = current_time(root);
340 s->s_root = d_make_root(root);
341 if (!s->s_root)
342 return -ENOMEM;
343 s->s_d_op = ctx->dops;
344 return 0;
345}
346
347static int pseudo_fs_get_tree(struct fs_context *fc)
348{
349 return get_tree_nodev(fc, pseudo_fs_fill_super);
350}
351
352static void pseudo_fs_free(struct fs_context *fc)
353{
354 kfree(fc->fs_private);
355}
356
357static const struct fs_context_operations pseudo_fs_context_ops = {
358 .free = pseudo_fs_free,
359 .get_tree = pseudo_fs_get_tree,
360};
361
362/*
363 * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
364 * will never be mountable)
365 */
366struct pseudo_fs_context *init_pseudo(struct fs_context *fc,
367 unsigned long magic)
368{
369 struct pseudo_fs_context *ctx;
370
371 ctx = kzalloc(sizeof(struct pseudo_fs_context), GFP_KERNEL);
372 if (likely(ctx)) {
373 ctx->magic = magic;
374 fc->fs_private = ctx;
375 fc->ops = &pseudo_fs_context_ops;
376 fc->sb_flags |= SB_NOUSER;
377 fc->global = true;
378 }
379 return ctx;
380}
381EXPORT_SYMBOL(init_pseudo);
382
383int simple_open(struct inode *inode, struct file *file)
384{
385 if (inode->i_private)
386 file->private_data = inode->i_private;
387 return 0;
388}
389EXPORT_SYMBOL(simple_open);
390
391int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
392{
393 struct inode *inode = d_inode(old_dentry);
394
395 inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
396 inc_nlink(inode);
397 ihold(inode);
398 dget(dentry);
399 d_instantiate(dentry, inode);
400 return 0;
401}
402EXPORT_SYMBOL(simple_link);
403
404int simple_empty(struct dentry *dentry)
405{
406 struct dentry *child;
407 int ret = 0;
408
409 spin_lock(&dentry->d_lock);
410 list_for_each_entry(child, &dentry->d_subdirs, d_child) {
411 spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
412 if (simple_positive(child)) {
413 spin_unlock(&child->d_lock);
414 goto out;
415 }
416 spin_unlock(&child->d_lock);
417 }
418 ret = 1;
419out:
420 spin_unlock(&dentry->d_lock);
421 return ret;
422}
423EXPORT_SYMBOL(simple_empty);
424
425int simple_unlink(struct inode *dir, struct dentry *dentry)
426{
427 struct inode *inode = d_inode(dentry);
428
429 inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
430 drop_nlink(inode);
431 dput(dentry);
432 return 0;
433}
434EXPORT_SYMBOL(simple_unlink);
435
436int simple_rmdir(struct inode *dir, struct dentry *dentry)
437{
438 if (!simple_empty(dentry))
439 return -ENOTEMPTY;
440
441 drop_nlink(d_inode(dentry));
442 simple_unlink(dir, dentry);
443 drop_nlink(dir);
444 return 0;
445}
446EXPORT_SYMBOL(simple_rmdir);
447
448int simple_rename(struct inode *old_dir, struct dentry *old_dentry,
449 struct inode *new_dir, struct dentry *new_dentry,
450 unsigned int flags)
451{
452 struct inode *inode = d_inode(old_dentry);
453 int they_are_dirs = d_is_dir(old_dentry);
454
455 if (flags & ~RENAME_NOREPLACE)
456 return -EINVAL;
457
458 if (!simple_empty(new_dentry))
459 return -ENOTEMPTY;
460
461 if (d_really_is_positive(new_dentry)) {
462 simple_unlink(new_dir, new_dentry);
463 if (they_are_dirs) {
464 drop_nlink(d_inode(new_dentry));
465 drop_nlink(old_dir);
466 }
467 } else if (they_are_dirs) {
468 drop_nlink(old_dir);
469 inc_nlink(new_dir);
470 }
471
472 old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime =
473 new_dir->i_mtime = inode->i_ctime = current_time(old_dir);
474
475 return 0;
476}
477EXPORT_SYMBOL(simple_rename);
478
479/**
480 * simple_setattr - setattr for simple filesystem
481 * @dentry: dentry
482 * @iattr: iattr structure
483 *
484 * Returns 0 on success, -error on failure.
485 *
486 * simple_setattr is a simple ->setattr implementation without a proper
487 * implementation of size changes.
488 *
489 * It can either be used for in-memory filesystems or special files
490 * on simple regular filesystems. Anything that needs to change on-disk
491 * or wire state on size changes needs its own setattr method.
492 */
493int simple_setattr(struct dentry *dentry, struct iattr *iattr)
494{
495 struct inode *inode = d_inode(dentry);
496 int error;
497
498 error = setattr_prepare(dentry, iattr);
499 if (error)
500 return error;
501
502 if (iattr->ia_valid & ATTR_SIZE)
503 truncate_setsize(inode, iattr->ia_size);
504 setattr_copy(inode, iattr);
505 mark_inode_dirty(inode);
506 return 0;
507}
508EXPORT_SYMBOL(simple_setattr);
509
510int simple_readpage(struct file *file, struct page *page)
511{
512 clear_highpage(page);
513 flush_dcache_page(page);
514 SetPageUptodate(page);
515 unlock_page(page);
516 return 0;
517}
518EXPORT_SYMBOL(simple_readpage);
519
520int simple_write_begin(struct file *file, struct address_space *mapping,
521 loff_t pos, unsigned len, unsigned flags,
522 struct page **pagep, void **fsdata)
523{
524 struct page *page;
525 pgoff_t index;
526
527 index = pos >> PAGE_SHIFT;
528
529 page = grab_cache_page_write_begin(mapping, index, flags);
530 if (!page)
531 return -ENOMEM;
532
533 *pagep = page;
534
535 if (!PageUptodate(page) && (len != PAGE_SIZE)) {
536 unsigned from = pos & (PAGE_SIZE - 1);
537
538 zero_user_segments(page, 0, from, from + len, PAGE_SIZE);
539 }
540 return 0;
541}
542EXPORT_SYMBOL(simple_write_begin);
543
544/**
545 * simple_write_end - .write_end helper for non-block-device FSes
546 * @file: See .write_end of address_space_operations
547 * @mapping: "
548 * @pos: "
549 * @len: "
550 * @copied: "
551 * @page: "
552 * @fsdata: "
553 *
554 * simple_write_end does the minimum needed for updating a page after writing is
555 * done. It has the same API signature as the .write_end of
556 * address_space_operations vector. So it can just be set onto .write_end for
557 * FSes that don't need any other processing. i_mutex is assumed to be held.
558 * Block based filesystems should use generic_write_end().
559 * NOTE: Even though i_size might get updated by this function, mark_inode_dirty
560 * is not called, so a filesystem that actually does store data in .write_inode
561 * should extend on what's done here with a call to mark_inode_dirty() in the
562 * case that i_size has changed.
563 *
564 * Use *ONLY* with simple_readpage()
565 */
566int simple_write_end(struct file *file, struct address_space *mapping,
567 loff_t pos, unsigned len, unsigned copied,
568 struct page *page, void *fsdata)
569{
570 struct inode *inode = page->mapping->host;
571 loff_t last_pos = pos + copied;
572
573 /* zero the stale part of the page if we did a short copy */
574 if (!PageUptodate(page)) {
575 if (copied < len) {
576 unsigned from = pos & (PAGE_SIZE - 1);
577
578 zero_user(page, from + copied, len - copied);
579 }
580 SetPageUptodate(page);
581 }
582 /*
583 * No need to use i_size_read() here, the i_size
584 * cannot change under us because we hold the i_mutex.
585 */
586 if (last_pos > inode->i_size)
587 i_size_write(inode, last_pos);
588
589 set_page_dirty(page);
590 unlock_page(page);
591 put_page(page);
592
593 return copied;
594}
595EXPORT_SYMBOL(simple_write_end);
596
597/*
598 * the inodes created here are not hashed. If you use iunique to generate
599 * unique inode values later for this filesystem, then you must take care
600 * to pass it an appropriate max_reserved value to avoid collisions.
601 */
602int simple_fill_super(struct super_block *s, unsigned long magic,
603 const struct tree_descr *files)
604{
605 struct inode *inode;
606 struct dentry *root;
607 struct dentry *dentry;
608 int i;
609
610 s->s_blocksize = PAGE_SIZE;
611 s->s_blocksize_bits = PAGE_SHIFT;
612 s->s_magic = magic;
613 s->s_op = &simple_super_operations;
614 s->s_time_gran = 1;
615
616 inode = new_inode(s);
617 if (!inode)
618 return -ENOMEM;
619 /*
620 * because the root inode is 1, the files array must not contain an
621 * entry at index 1
622 */
623 inode->i_ino = 1;
624 inode->i_mode = S_IFDIR | 0755;
625 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
626 inode->i_op = &simple_dir_inode_operations;
627 inode->i_fop = &simple_dir_operations;
628 set_nlink(inode, 2);
629 root = d_make_root(inode);
630 if (!root)
631 return -ENOMEM;
632 for (i = 0; !files->name || files->name[0]; i++, files++) {
633 if (!files->name)
634 continue;
635
636 /* warn if it tries to conflict with the root inode */
637 if (unlikely(i == 1))
638 printk(KERN_WARNING "%s: %s passed in a files array"
639 "with an index of 1!\n", __func__,
640 s->s_type->name);
641
642 dentry = d_alloc_name(root, files->name);
643 if (!dentry)
644 goto out;
645 inode = new_inode(s);
646 if (!inode) {
647 dput(dentry);
648 goto out;
649 }
650 inode->i_mode = S_IFREG | files->mode;
651 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
652 inode->i_fop = files->ops;
653 inode->i_ino = i;
654 d_add(dentry, inode);
655 }
656 s->s_root = root;
657 return 0;
658out:
659 d_genocide(root);
660 shrink_dcache_parent(root);
661 dput(root);
662 return -ENOMEM;
663}
664EXPORT_SYMBOL(simple_fill_super);
665
666static DEFINE_SPINLOCK(pin_fs_lock);
667
668int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count)
669{
670 struct vfsmount *mnt = NULL;
671 spin_lock(&pin_fs_lock);
672 if (unlikely(!*mount)) {
673 spin_unlock(&pin_fs_lock);
674 mnt = vfs_kern_mount(type, SB_KERNMOUNT, type->name, NULL);
675 if (IS_ERR(mnt))
676 return PTR_ERR(mnt);
677 spin_lock(&pin_fs_lock);
678 if (!*mount)
679 *mount = mnt;
680 }
681 mntget(*mount);
682 ++*count;
683 spin_unlock(&pin_fs_lock);
684 mntput(mnt);
685 return 0;
686}
687EXPORT_SYMBOL(simple_pin_fs);
688
689void simple_release_fs(struct vfsmount **mount, int *count)
690{
691 struct vfsmount *mnt;
692 spin_lock(&pin_fs_lock);
693 mnt = *mount;
694 if (!--*count)
695 *mount = NULL;
696 spin_unlock(&pin_fs_lock);
697 mntput(mnt);
698}
699EXPORT_SYMBOL(simple_release_fs);
700
701/**
702 * simple_read_from_buffer - copy data from the buffer to user space
703 * @to: the user space buffer to read to
704 * @count: the maximum number of bytes to read
705 * @ppos: the current position in the buffer
706 * @from: the buffer to read from
707 * @available: the size of the buffer
708 *
709 * The simple_read_from_buffer() function reads up to @count bytes from the
710 * buffer @from at offset @ppos into the user space address starting at @to.
711 *
712 * On success, the number of bytes read is returned and the offset @ppos is
713 * advanced by this number, or negative value is returned on error.
714 **/
715ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
716 const void *from, size_t available)
717{
718 loff_t pos = *ppos;
719 size_t ret;
720
721 if (pos < 0)
722 return -EINVAL;
723 if (pos >= available || !count)
724 return 0;
725 if (count > available - pos)
726 count = available - pos;
727 ret = copy_to_user(to, from + pos, count);
728 if (ret == count)
729 return -EFAULT;
730 count -= ret;
731 *ppos = pos + count;
732 return count;
733}
734EXPORT_SYMBOL(simple_read_from_buffer);
735
736/**
737 * simple_write_to_buffer - copy data from user space to the buffer
738 * @to: the buffer to write to
739 * @available: the size of the buffer
740 * @ppos: the current position in the buffer
741 * @from: the user space buffer to read from
742 * @count: the maximum number of bytes to read
743 *
744 * The simple_write_to_buffer() function reads up to @count bytes from the user
745 * space address starting at @from into the buffer @to at offset @ppos.
746 *
747 * On success, the number of bytes written is returned and the offset @ppos is
748 * advanced by this number, or negative value is returned on error.
749 **/
750ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
751 const void __user *from, size_t count)
752{
753 loff_t pos = *ppos;
754 size_t res;
755
756 if (pos < 0)
757 return -EINVAL;
758 if (pos >= available || !count)
759 return 0;
760 if (count > available - pos)
761 count = available - pos;
762 res = copy_from_user(to + pos, from, count);
763 if (res == count)
764 return -EFAULT;
765 count -= res;
766 *ppos = pos + count;
767 return count;
768}
769EXPORT_SYMBOL(simple_write_to_buffer);
770
771/**
772 * memory_read_from_buffer - copy data from the buffer
773 * @to: the kernel space buffer to read to
774 * @count: the maximum number of bytes to read
775 * @ppos: the current position in the buffer
776 * @from: the buffer to read from
777 * @available: the size of the buffer
778 *
779 * The memory_read_from_buffer() function reads up to @count bytes from the
780 * buffer @from at offset @ppos into the kernel space address starting at @to.
781 *
782 * On success, the number of bytes read is returned and the offset @ppos is
783 * advanced by this number, or negative value is returned on error.
784 **/
785ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
786 const void *from, size_t available)
787{
788 loff_t pos = *ppos;
789
790 if (pos < 0)
791 return -EINVAL;
792 if (pos >= available)
793 return 0;
794 if (count > available - pos)
795 count = available - pos;
796 memcpy(to, from + pos, count);
797 *ppos = pos + count;
798
799 return count;
800}
801EXPORT_SYMBOL(memory_read_from_buffer);
802
803/*
804 * Transaction based IO.
805 * The file expects a single write which triggers the transaction, and then
806 * possibly a read which collects the result - which is stored in a
807 * file-local buffer.
808 */
809
810void simple_transaction_set(struct file *file, size_t n)
811{
812 struct simple_transaction_argresp *ar = file->private_data;
813
814 BUG_ON(n > SIMPLE_TRANSACTION_LIMIT);
815
816 /*
817 * The barrier ensures that ar->size will really remain zero until
818 * ar->data is ready for reading.
819 */
820 smp_mb();
821 ar->size = n;
822}
823EXPORT_SYMBOL(simple_transaction_set);
824
825char *simple_transaction_get(struct file *file, const char __user *buf, size_t size)
826{
827 struct simple_transaction_argresp *ar;
828 static DEFINE_SPINLOCK(simple_transaction_lock);
829
830 if (size > SIMPLE_TRANSACTION_LIMIT - 1)
831 return ERR_PTR(-EFBIG);
832
833 ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL);
834 if (!ar)
835 return ERR_PTR(-ENOMEM);
836
837 spin_lock(&simple_transaction_lock);
838
839 /* only one write allowed per open */
840 if (file->private_data) {
841 spin_unlock(&simple_transaction_lock);
842 free_page((unsigned long)ar);
843 return ERR_PTR(-EBUSY);
844 }
845
846 file->private_data = ar;
847
848 spin_unlock(&simple_transaction_lock);
849
850 if (copy_from_user(ar->data, buf, size))
851 return ERR_PTR(-EFAULT);
852
853 return ar->data;
854}
855EXPORT_SYMBOL(simple_transaction_get);
856
857ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos)
858{
859 struct simple_transaction_argresp *ar = file->private_data;
860
861 if (!ar)
862 return 0;
863 return simple_read_from_buffer(buf, size, pos, ar->data, ar->size);
864}
865EXPORT_SYMBOL(simple_transaction_read);
866
867int simple_transaction_release(struct inode *inode, struct file *file)
868{
869 free_page((unsigned long)file->private_data);
870 return 0;
871}
872EXPORT_SYMBOL(simple_transaction_release);
873
874/* Simple attribute files */
875
876struct simple_attr {
877 int (*get)(void *, u64 *);
878 int (*set)(void *, u64);
879 char get_buf[24]; /* enough to store a u64 and "\n\0" */
880 char set_buf[24];
881 void *data;
882 const char *fmt; /* format for read operation */
883 struct mutex mutex; /* protects access to these buffers */
884};
885
886/* simple_attr_open is called by an actual attribute open file operation
887 * to set the attribute specific access operations. */
888int simple_attr_open(struct inode *inode, struct file *file,
889 int (*get)(void *, u64 *), int (*set)(void *, u64),
890 const char *fmt)
891{
892 struct simple_attr *attr;
893
894 attr = kzalloc(sizeof(*attr), GFP_KERNEL);
895 if (!attr)
896 return -ENOMEM;
897
898 attr->get = get;
899 attr->set = set;
900 attr->data = inode->i_private;
901 attr->fmt = fmt;
902 mutex_init(&attr->mutex);
903
904 file->private_data = attr;
905
906 return nonseekable_open(inode, file);
907}
908EXPORT_SYMBOL_GPL(simple_attr_open);
909
910int simple_attr_release(struct inode *inode, struct file *file)
911{
912 kfree(file->private_data);
913 return 0;
914}
915EXPORT_SYMBOL_GPL(simple_attr_release); /* GPL-only? This? Really? */
916
917/* read from the buffer that is filled with the get function */
918ssize_t simple_attr_read(struct file *file, char __user *buf,
919 size_t len, loff_t *ppos)
920{
921 struct simple_attr *attr;
922 size_t size;
923 ssize_t ret;
924
925 attr = file->private_data;
926
927 if (!attr->get)
928 return -EACCES;
929
930 ret = mutex_lock_interruptible(&attr->mutex);
931 if (ret)
932 return ret;
933
934 if (*ppos && attr->get_buf[0]) {
935 /* continued read */
936 size = strlen(attr->get_buf);
937 } else {
938 /* first read */
939 u64 val;
940 ret = attr->get(attr->data, &val);
941 if (ret)
942 goto out;
943
944 size = scnprintf(attr->get_buf, sizeof(attr->get_buf),
945 attr->fmt, (unsigned long long)val);
946 }
947
948 ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
949out:
950 mutex_unlock(&attr->mutex);
951 return ret;
952}
953EXPORT_SYMBOL_GPL(simple_attr_read);
954
955/* interpret the buffer as a number to call the set function with */
956ssize_t simple_attr_write(struct file *file, const char __user *buf,
957 size_t len, loff_t *ppos)
958{
959 struct simple_attr *attr;
960 u64 val;
961 size_t size;
962 ssize_t ret;
963
964 attr = file->private_data;
965 if (!attr->set)
966 return -EACCES;
967
968 ret = mutex_lock_interruptible(&attr->mutex);
969 if (ret)
970 return ret;
971
972 ret = -EFAULT;
973 size = min(sizeof(attr->set_buf) - 1, len);
974 if (copy_from_user(attr->set_buf, buf, size))
975 goto out;
976
977 attr->set_buf[size] = '\0';
978 val = simple_strtoll(attr->set_buf, NULL, 0);
979 ret = attr->set(attr->data, val);
980 if (ret == 0)
981 ret = len; /* on success, claim we got the whole input */
982out:
983 mutex_unlock(&attr->mutex);
984 return ret;
985}
986EXPORT_SYMBOL_GPL(simple_attr_write);
987
988/**
989 * generic_fh_to_dentry - generic helper for the fh_to_dentry export operation
990 * @sb: filesystem to do the file handle conversion on
991 * @fid: file handle to convert
992 * @fh_len: length of the file handle in bytes
993 * @fh_type: type of file handle
994 * @get_inode: filesystem callback to retrieve inode
995 *
996 * This function decodes @fid as long as it has one of the well-known
997 * Linux filehandle types and calls @get_inode on it to retrieve the
998 * inode for the object specified in the file handle.
999 */
1000struct dentry *generic_fh_to_dentry(struct super_block *sb, struct fid *fid,
1001 int fh_len, int fh_type, struct inode *(*get_inode)
1002 (struct super_block *sb, u64 ino, u32 gen))
1003{
1004 struct inode *inode = NULL;
1005
1006 if (fh_len < 2)
1007 return NULL;
1008
1009 switch (fh_type) {
1010 case FILEID_INO32_GEN:
1011 case FILEID_INO32_GEN_PARENT:
1012 inode = get_inode(sb, fid->i32.ino, fid->i32.gen);
1013 break;
1014 }
1015
1016 return d_obtain_alias(inode);
1017}
1018EXPORT_SYMBOL_GPL(generic_fh_to_dentry);
1019
1020/**
1021 * generic_fh_to_parent - generic helper for the fh_to_parent export operation
1022 * @sb: filesystem to do the file handle conversion on
1023 * @fid: file handle to convert
1024 * @fh_len: length of the file handle in bytes
1025 * @fh_type: type of file handle
1026 * @get_inode: filesystem callback to retrieve inode
1027 *
1028 * This function decodes @fid as long as it has one of the well-known
1029 * Linux filehandle types and calls @get_inode on it to retrieve the
1030 * inode for the _parent_ object specified in the file handle if it
1031 * is specified in the file handle, or NULL otherwise.
1032 */
1033struct dentry *generic_fh_to_parent(struct super_block *sb, struct fid *fid,
1034 int fh_len, int fh_type, struct inode *(*get_inode)
1035 (struct super_block *sb, u64 ino, u32 gen))
1036{
1037 struct inode *inode = NULL;
1038
1039 if (fh_len <= 2)
1040 return NULL;
1041
1042 switch (fh_type) {
1043 case FILEID_INO32_GEN_PARENT:
1044 inode = get_inode(sb, fid->i32.parent_ino,
1045 (fh_len > 3 ? fid->i32.parent_gen : 0));
1046 break;
1047 }
1048
1049 return d_obtain_alias(inode);
1050}
1051EXPORT_SYMBOL_GPL(generic_fh_to_parent);
1052
1053/**
1054 * __generic_file_fsync - generic fsync implementation for simple filesystems
1055 *
1056 * @file: file to synchronize
1057 * @start: start offset in bytes
1058 * @end: end offset in bytes (inclusive)
1059 * @datasync: only synchronize essential metadata if true
1060 *
1061 * This is a generic implementation of the fsync method for simple
1062 * filesystems which track all non-inode metadata in the buffers list
1063 * hanging off the address_space structure.
1064 */
1065int __generic_file_fsync(struct file *file, loff_t start, loff_t end,
1066 int datasync)
1067{
1068 struct inode *inode = file->f_mapping->host;
1069 int err;
1070 int ret;
1071
1072 err = file_write_and_wait_range(file, start, end);
1073 if (err)
1074 return err;
1075
1076 inode_lock(inode);
1077 ret = sync_mapping_buffers(inode->i_mapping);
1078 if (!(inode->i_state & I_DIRTY_ALL))
1079 goto out;
1080 if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
1081 goto out;
1082
1083 err = sync_inode_metadata(inode, 1);
1084 if (ret == 0)
1085 ret = err;
1086
1087out:
1088 inode_unlock(inode);
1089 /* check and advance again to catch errors after syncing out buffers */
1090 err = file_check_and_advance_wb_err(file);
1091 if (ret == 0)
1092 ret = err;
1093 return ret;
1094}
1095EXPORT_SYMBOL(__generic_file_fsync);
1096
1097/**
1098 * generic_file_fsync - generic fsync implementation for simple filesystems
1099 * with flush
1100 * @file: file to synchronize
1101 * @start: start offset in bytes
1102 * @end: end offset in bytes (inclusive)
1103 * @datasync: only synchronize essential metadata if true
1104 *
1105 */
1106
1107int generic_file_fsync(struct file *file, loff_t start, loff_t end,
1108 int datasync)
1109{
1110 struct inode *inode = file->f_mapping->host;
1111 int err;
1112
1113 err = __generic_file_fsync(file, start, end, datasync);
1114 if (err)
1115 return err;
1116 return blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL);
1117}
1118EXPORT_SYMBOL(generic_file_fsync);
1119
1120/**
1121 * generic_check_addressable - Check addressability of file system
1122 * @blocksize_bits: log of file system block size
1123 * @num_blocks: number of blocks in file system
1124 *
1125 * Determine whether a file system with @num_blocks blocks (and a
1126 * block size of 2**@blocksize_bits) is addressable by the sector_t
1127 * and page cache of the system. Return 0 if so and -EFBIG otherwise.
1128 */
1129int generic_check_addressable(unsigned blocksize_bits, u64 num_blocks)
1130{
1131 u64 last_fs_block = num_blocks - 1;
1132 u64 last_fs_page =
1133 last_fs_block >> (PAGE_SHIFT - blocksize_bits);
1134
1135 if (unlikely(num_blocks == 0))
1136 return 0;
1137
1138 if ((blocksize_bits < 9) || (blocksize_bits > PAGE_SHIFT))
1139 return -EINVAL;
1140
1141 if ((last_fs_block > (sector_t)(~0ULL) >> (blocksize_bits - 9)) ||
1142 (last_fs_page > (pgoff_t)(~0ULL))) {
1143 return -EFBIG;
1144 }
1145 return 0;
1146}
1147EXPORT_SYMBOL(generic_check_addressable);
1148
1149/*
1150 * No-op implementation of ->fsync for in-memory filesystems.
1151 */
1152int noop_fsync(struct file *file, loff_t start, loff_t end, int datasync)
1153{
1154 return 0;
1155}
1156EXPORT_SYMBOL(noop_fsync);
1157
1158int noop_set_page_dirty(struct page *page)
1159{
1160 /*
1161 * Unlike __set_page_dirty_no_writeback that handles dirty page
1162 * tracking in the page object, dax does all dirty tracking in
1163 * the inode address_space in response to mkwrite faults. In the
1164 * dax case we only need to worry about potentially dirty CPU
1165 * caches, not dirty page cache pages to write back.
1166 *
1167 * This callback is defined to prevent fallback to
1168 * __set_page_dirty_buffers() in set_page_dirty().
1169 */
1170 return 0;
1171}
1172EXPORT_SYMBOL_GPL(noop_set_page_dirty);
1173
1174void noop_invalidatepage(struct page *page, unsigned int offset,
1175 unsigned int length)
1176{
1177 /*
1178 * There is no page cache to invalidate in the dax case, however
1179 * we need this callback defined to prevent falling back to
1180 * block_invalidatepage() in do_invalidatepage().
1181 */
1182}
1183EXPORT_SYMBOL_GPL(noop_invalidatepage);
1184
1185ssize_t noop_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
1186{
1187 /*
1188 * iomap based filesystems support direct I/O without need for
1189 * this callback. However, it still needs to be set in
1190 * inode->a_ops so that open/fcntl know that direct I/O is
1191 * generally supported.
1192 */
1193 return -EINVAL;
1194}
1195EXPORT_SYMBOL_GPL(noop_direct_IO);
1196
1197/* Because kfree isn't assignment-compatible with void(void*) ;-/ */
1198void kfree_link(void *p)
1199{
1200 kfree(p);
1201}
1202EXPORT_SYMBOL(kfree_link);
1203
1204/*
1205 * nop .set_page_dirty method so that people can use .page_mkwrite on
1206 * anon inodes.
1207 */
1208static int anon_set_page_dirty(struct page *page)
1209{
1210 return 0;
1211};
1212
1213/*
1214 * A single inode exists for all anon_inode files. Contrary to pipes,
1215 * anon_inode inodes have no associated per-instance data, so we need
1216 * only allocate one of them.
1217 */
1218struct inode *alloc_anon_inode(struct super_block *s)
1219{
1220 static const struct address_space_operations anon_aops = {
1221 .set_page_dirty = anon_set_page_dirty,
1222 };
1223 struct inode *inode = new_inode_pseudo(s);
1224
1225 if (!inode)
1226 return ERR_PTR(-ENOMEM);
1227
1228 inode->i_ino = get_next_ino();
1229 inode->i_mapping->a_ops = &anon_aops;
1230
1231 /*
1232 * Mark the inode dirty from the very beginning,
1233 * that way it will never be moved to the dirty
1234 * list because mark_inode_dirty() will think
1235 * that it already _is_ on the dirty list.
1236 */
1237 inode->i_state = I_DIRTY;
1238 inode->i_mode = S_IRUSR | S_IWUSR;
1239 inode->i_uid = current_fsuid();
1240 inode->i_gid = current_fsgid();
1241 inode->i_flags |= S_PRIVATE;
1242 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
1243 return inode;
1244}
1245EXPORT_SYMBOL(alloc_anon_inode);
1246
1247/**
1248 * simple_nosetlease - generic helper for prohibiting leases
1249 * @filp: file pointer
1250 * @arg: type of lease to obtain
1251 * @flp: new lease supplied for insertion
1252 * @priv: private data for lm_setup operation
1253 *
1254 * Generic helper for filesystems that do not wish to allow leases to be set.
1255 * All arguments are ignored and it just returns -EINVAL.
1256 */
1257int
1258simple_nosetlease(struct file *filp, long arg, struct file_lock **flp,
1259 void **priv)
1260{
1261 return -EINVAL;
1262}
1263EXPORT_SYMBOL(simple_nosetlease);
1264
1265/**
1266 * simple_get_link - generic helper to get the target of "fast" symlinks
1267 * @dentry: not used here
1268 * @inode: the symlink inode
1269 * @done: not used here
1270 *
1271 * Generic helper for filesystems to use for symlink inodes where a pointer to
1272 * the symlink target is stored in ->i_link. NOTE: this isn't normally called,
1273 * since as an optimization the path lookup code uses any non-NULL ->i_link
1274 * directly, without calling ->get_link(). But ->get_link() still must be set,
1275 * to mark the inode_operations as being for a symlink.
1276 *
1277 * Return: the symlink target
1278 */
1279const char *simple_get_link(struct dentry *dentry, struct inode *inode,
1280 struct delayed_call *done)
1281{
1282 return inode->i_link;
1283}
1284EXPORT_SYMBOL(simple_get_link);
1285
1286const struct inode_operations simple_symlink_inode_operations = {
1287 .get_link = simple_get_link,
1288};
1289EXPORT_SYMBOL(simple_symlink_inode_operations);
1290
1291/*
1292 * Operations for a permanently empty directory.
1293 */
1294static struct dentry *empty_dir_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
1295{
1296 return ERR_PTR(-ENOENT);
1297}
1298
1299static int empty_dir_getattr(const struct path *path, struct kstat *stat,
1300 u32 request_mask, unsigned int query_flags)
1301{
1302 struct inode *inode = d_inode(path->dentry);
1303 generic_fillattr(inode, stat);
1304 return 0;
1305}
1306
1307static int empty_dir_setattr(struct dentry *dentry, struct iattr *attr)
1308{
1309 return -EPERM;
1310}
1311
1312static ssize_t empty_dir_listxattr(struct dentry *dentry, char *list, size_t size)
1313{
1314 return -EOPNOTSUPP;
1315}
1316
1317static const struct inode_operations empty_dir_inode_operations = {
1318 .lookup = empty_dir_lookup,
1319 .permission = generic_permission,
1320 .setattr = empty_dir_setattr,
1321 .getattr = empty_dir_getattr,
1322 .listxattr = empty_dir_listxattr,
1323};
1324
1325static loff_t empty_dir_llseek(struct file *file, loff_t offset, int whence)
1326{
1327 /* An empty directory has two entries . and .. at offsets 0 and 1 */
1328 return generic_file_llseek_size(file, offset, whence, 2, 2);
1329}
1330
1331static int empty_dir_readdir(struct file *file, struct dir_context *ctx)
1332{
1333 dir_emit_dots(file, ctx);
1334 return 0;
1335}
1336
1337static const struct file_operations empty_dir_operations = {
1338 .llseek = empty_dir_llseek,
1339 .read = generic_read_dir,
1340 .iterate_shared = empty_dir_readdir,
1341 .fsync = noop_fsync,
1342};
1343
1344
1345void make_empty_dir_inode(struct inode *inode)
1346{
1347 set_nlink(inode, 2);
1348 inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO;
1349 inode->i_uid = GLOBAL_ROOT_UID;
1350 inode->i_gid = GLOBAL_ROOT_GID;
1351 inode->i_rdev = 0;
1352 inode->i_size = 0;
1353 inode->i_blkbits = PAGE_SHIFT;
1354 inode->i_blocks = 0;
1355
1356 inode->i_op = &empty_dir_inode_operations;
1357 inode->i_opflags &= ~IOP_XATTR;
1358 inode->i_fop = &empty_dir_operations;
1359}
1360
1361bool is_empty_dir_inode(struct inode *inode)
1362{
1363 return (inode->i_fop == &empty_dir_operations) &&
1364 (inode->i_op == &empty_dir_inode_operations);
1365}
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * fs/libfs.c
4 * Library for filesystems writers.
5 */
6
7#include <linux/blkdev.h>
8#include <linux/export.h>
9#include <linux/pagemap.h>
10#include <linux/slab.h>
11#include <linux/cred.h>
12#include <linux/mount.h>
13#include <linux/vfs.h>
14#include <linux/quotaops.h>
15#include <linux/mutex.h>
16#include <linux/namei.h>
17#include <linux/exportfs.h>
18#include <linux/iversion.h>
19#include <linux/writeback.h>
20#include <linux/buffer_head.h> /* sync_mapping_buffers */
21#include <linux/fs_context.h>
22#include <linux/pseudo_fs.h>
23#include <linux/fsnotify.h>
24#include <linux/unicode.h>
25#include <linux/fscrypt.h>
26
27#include <linux/uaccess.h>
28
29#include "internal.h"
30
31int simple_getattr(struct user_namespace *mnt_userns, const struct path *path,
32 struct kstat *stat, u32 request_mask,
33 unsigned int query_flags)
34{
35 struct inode *inode = d_inode(path->dentry);
36 generic_fillattr(&init_user_ns, inode, stat);
37 stat->blocks = inode->i_mapping->nrpages << (PAGE_SHIFT - 9);
38 return 0;
39}
40EXPORT_SYMBOL(simple_getattr);
41
42int simple_statfs(struct dentry *dentry, struct kstatfs *buf)
43{
44 buf->f_type = dentry->d_sb->s_magic;
45 buf->f_bsize = PAGE_SIZE;
46 buf->f_namelen = NAME_MAX;
47 return 0;
48}
49EXPORT_SYMBOL(simple_statfs);
50
51/*
52 * Retaining negative dentries for an in-memory filesystem just wastes
53 * memory and lookup time: arrange for them to be deleted immediately.
54 */
55int always_delete_dentry(const struct dentry *dentry)
56{
57 return 1;
58}
59EXPORT_SYMBOL(always_delete_dentry);
60
61const struct dentry_operations simple_dentry_operations = {
62 .d_delete = always_delete_dentry,
63};
64EXPORT_SYMBOL(simple_dentry_operations);
65
66/*
67 * Lookup the data. This is trivial - if the dentry didn't already
68 * exist, we know it is negative. Set d_op to delete negative dentries.
69 */
70struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
71{
72 if (dentry->d_name.len > NAME_MAX)
73 return ERR_PTR(-ENAMETOOLONG);
74 if (!dentry->d_sb->s_d_op)
75 d_set_d_op(dentry, &simple_dentry_operations);
76 d_add(dentry, NULL);
77 return NULL;
78}
79EXPORT_SYMBOL(simple_lookup);
80
81int dcache_dir_open(struct inode *inode, struct file *file)
82{
83 file->private_data = d_alloc_cursor(file->f_path.dentry);
84
85 return file->private_data ? 0 : -ENOMEM;
86}
87EXPORT_SYMBOL(dcache_dir_open);
88
89int dcache_dir_close(struct inode *inode, struct file *file)
90{
91 dput(file->private_data);
92 return 0;
93}
94EXPORT_SYMBOL(dcache_dir_close);
95
96/* parent is locked at least shared */
97/*
98 * Returns an element of siblings' list.
99 * We are looking for <count>th positive after <p>; if
100 * found, dentry is grabbed and returned to caller.
101 * If no such element exists, NULL is returned.
102 */
103static struct dentry *scan_positives(struct dentry *cursor,
104 struct list_head *p,
105 loff_t count,
106 struct dentry *last)
107{
108 struct dentry *dentry = cursor->d_parent, *found = NULL;
109
110 spin_lock(&dentry->d_lock);
111 while ((p = p->next) != &dentry->d_subdirs) {
112 struct dentry *d = list_entry(p, struct dentry, d_child);
113 // we must at least skip cursors, to avoid livelocks
114 if (d->d_flags & DCACHE_DENTRY_CURSOR)
115 continue;
116 if (simple_positive(d) && !--count) {
117 spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
118 if (simple_positive(d))
119 found = dget_dlock(d);
120 spin_unlock(&d->d_lock);
121 if (likely(found))
122 break;
123 count = 1;
124 }
125 if (need_resched()) {
126 list_move(&cursor->d_child, p);
127 p = &cursor->d_child;
128 spin_unlock(&dentry->d_lock);
129 cond_resched();
130 spin_lock(&dentry->d_lock);
131 }
132 }
133 spin_unlock(&dentry->d_lock);
134 dput(last);
135 return found;
136}
137
138loff_t dcache_dir_lseek(struct file *file, loff_t offset, int whence)
139{
140 struct dentry *dentry = file->f_path.dentry;
141 switch (whence) {
142 case 1:
143 offset += file->f_pos;
144 fallthrough;
145 case 0:
146 if (offset >= 0)
147 break;
148 fallthrough;
149 default:
150 return -EINVAL;
151 }
152 if (offset != file->f_pos) {
153 struct dentry *cursor = file->private_data;
154 struct dentry *to = NULL;
155
156 inode_lock_shared(dentry->d_inode);
157
158 if (offset > 2)
159 to = scan_positives(cursor, &dentry->d_subdirs,
160 offset - 2, NULL);
161 spin_lock(&dentry->d_lock);
162 if (to)
163 list_move(&cursor->d_child, &to->d_child);
164 else
165 list_del_init(&cursor->d_child);
166 spin_unlock(&dentry->d_lock);
167 dput(to);
168
169 file->f_pos = offset;
170
171 inode_unlock_shared(dentry->d_inode);
172 }
173 return offset;
174}
175EXPORT_SYMBOL(dcache_dir_lseek);
176
177/* Relationship between i_mode and the DT_xxx types */
178static inline unsigned char dt_type(struct inode *inode)
179{
180 return (inode->i_mode >> 12) & 15;
181}
182
183/*
184 * Directory is locked and all positive dentries in it are safe, since
185 * for ramfs-type trees they can't go away without unlink() or rmdir(),
186 * both impossible due to the lock on directory.
187 */
188
189int dcache_readdir(struct file *file, struct dir_context *ctx)
190{
191 struct dentry *dentry = file->f_path.dentry;
192 struct dentry *cursor = file->private_data;
193 struct list_head *anchor = &dentry->d_subdirs;
194 struct dentry *next = NULL;
195 struct list_head *p;
196
197 if (!dir_emit_dots(file, ctx))
198 return 0;
199
200 if (ctx->pos == 2)
201 p = anchor;
202 else if (!list_empty(&cursor->d_child))
203 p = &cursor->d_child;
204 else
205 return 0;
206
207 while ((next = scan_positives(cursor, p, 1, next)) != NULL) {
208 if (!dir_emit(ctx, next->d_name.name, next->d_name.len,
209 d_inode(next)->i_ino, dt_type(d_inode(next))))
210 break;
211 ctx->pos++;
212 p = &next->d_child;
213 }
214 spin_lock(&dentry->d_lock);
215 if (next)
216 list_move_tail(&cursor->d_child, &next->d_child);
217 else
218 list_del_init(&cursor->d_child);
219 spin_unlock(&dentry->d_lock);
220 dput(next);
221
222 return 0;
223}
224EXPORT_SYMBOL(dcache_readdir);
225
226ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
227{
228 return -EISDIR;
229}
230EXPORT_SYMBOL(generic_read_dir);
231
232const struct file_operations simple_dir_operations = {
233 .open = dcache_dir_open,
234 .release = dcache_dir_close,
235 .llseek = dcache_dir_lseek,
236 .read = generic_read_dir,
237 .iterate_shared = dcache_readdir,
238 .fsync = noop_fsync,
239};
240EXPORT_SYMBOL(simple_dir_operations);
241
242const struct inode_operations simple_dir_inode_operations = {
243 .lookup = simple_lookup,
244};
245EXPORT_SYMBOL(simple_dir_inode_operations);
246
247static struct dentry *find_next_child(struct dentry *parent, struct dentry *prev)
248{
249 struct dentry *child = NULL;
250 struct list_head *p = prev ? &prev->d_child : &parent->d_subdirs;
251
252 spin_lock(&parent->d_lock);
253 while ((p = p->next) != &parent->d_subdirs) {
254 struct dentry *d = container_of(p, struct dentry, d_child);
255 if (simple_positive(d)) {
256 spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
257 if (simple_positive(d))
258 child = dget_dlock(d);
259 spin_unlock(&d->d_lock);
260 if (likely(child))
261 break;
262 }
263 }
264 spin_unlock(&parent->d_lock);
265 dput(prev);
266 return child;
267}
268
269void simple_recursive_removal(struct dentry *dentry,
270 void (*callback)(struct dentry *))
271{
272 struct dentry *this = dget(dentry);
273 while (true) {
274 struct dentry *victim = NULL, *child;
275 struct inode *inode = this->d_inode;
276
277 inode_lock(inode);
278 if (d_is_dir(this))
279 inode->i_flags |= S_DEAD;
280 while ((child = find_next_child(this, victim)) == NULL) {
281 // kill and ascend
282 // update metadata while it's still locked
283 inode->i_ctime = current_time(inode);
284 clear_nlink(inode);
285 inode_unlock(inode);
286 victim = this;
287 this = this->d_parent;
288 inode = this->d_inode;
289 inode_lock(inode);
290 if (simple_positive(victim)) {
291 d_invalidate(victim); // avoid lost mounts
292 if (d_is_dir(victim))
293 fsnotify_rmdir(inode, victim);
294 else
295 fsnotify_unlink(inode, victim);
296 if (callback)
297 callback(victim);
298 dput(victim); // unpin it
299 }
300 if (victim == dentry) {
301 inode->i_ctime = inode->i_mtime =
302 current_time(inode);
303 if (d_is_dir(dentry))
304 drop_nlink(inode);
305 inode_unlock(inode);
306 dput(dentry);
307 return;
308 }
309 }
310 inode_unlock(inode);
311 this = child;
312 }
313}
314EXPORT_SYMBOL(simple_recursive_removal);
315
316static const struct super_operations simple_super_operations = {
317 .statfs = simple_statfs,
318};
319
320static int pseudo_fs_fill_super(struct super_block *s, struct fs_context *fc)
321{
322 struct pseudo_fs_context *ctx = fc->fs_private;
323 struct inode *root;
324
325 s->s_maxbytes = MAX_LFS_FILESIZE;
326 s->s_blocksize = PAGE_SIZE;
327 s->s_blocksize_bits = PAGE_SHIFT;
328 s->s_magic = ctx->magic;
329 s->s_op = ctx->ops ?: &simple_super_operations;
330 s->s_xattr = ctx->xattr;
331 s->s_time_gran = 1;
332 root = new_inode(s);
333 if (!root)
334 return -ENOMEM;
335
336 /*
337 * since this is the first inode, make it number 1. New inodes created
338 * after this must take care not to collide with it (by passing
339 * max_reserved of 1 to iunique).
340 */
341 root->i_ino = 1;
342 root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
343 root->i_atime = root->i_mtime = root->i_ctime = current_time(root);
344 s->s_root = d_make_root(root);
345 if (!s->s_root)
346 return -ENOMEM;
347 s->s_d_op = ctx->dops;
348 return 0;
349}
350
351static int pseudo_fs_get_tree(struct fs_context *fc)
352{
353 return get_tree_nodev(fc, pseudo_fs_fill_super);
354}
355
356static void pseudo_fs_free(struct fs_context *fc)
357{
358 kfree(fc->fs_private);
359}
360
361static const struct fs_context_operations pseudo_fs_context_ops = {
362 .free = pseudo_fs_free,
363 .get_tree = pseudo_fs_get_tree,
364};
365
366/*
367 * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
368 * will never be mountable)
369 */
370struct pseudo_fs_context *init_pseudo(struct fs_context *fc,
371 unsigned long magic)
372{
373 struct pseudo_fs_context *ctx;
374
375 ctx = kzalloc(sizeof(struct pseudo_fs_context), GFP_KERNEL);
376 if (likely(ctx)) {
377 ctx->magic = magic;
378 fc->fs_private = ctx;
379 fc->ops = &pseudo_fs_context_ops;
380 fc->sb_flags |= SB_NOUSER;
381 fc->global = true;
382 }
383 return ctx;
384}
385EXPORT_SYMBOL(init_pseudo);
386
387int simple_open(struct inode *inode, struct file *file)
388{
389 if (inode->i_private)
390 file->private_data = inode->i_private;
391 return 0;
392}
393EXPORT_SYMBOL(simple_open);
394
395int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
396{
397 struct inode *inode = d_inode(old_dentry);
398
399 inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
400 inc_nlink(inode);
401 ihold(inode);
402 dget(dentry);
403 d_instantiate(dentry, inode);
404 return 0;
405}
406EXPORT_SYMBOL(simple_link);
407
408int simple_empty(struct dentry *dentry)
409{
410 struct dentry *child;
411 int ret = 0;
412
413 spin_lock(&dentry->d_lock);
414 list_for_each_entry(child, &dentry->d_subdirs, d_child) {
415 spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
416 if (simple_positive(child)) {
417 spin_unlock(&child->d_lock);
418 goto out;
419 }
420 spin_unlock(&child->d_lock);
421 }
422 ret = 1;
423out:
424 spin_unlock(&dentry->d_lock);
425 return ret;
426}
427EXPORT_SYMBOL(simple_empty);
428
429int simple_unlink(struct inode *dir, struct dentry *dentry)
430{
431 struct inode *inode = d_inode(dentry);
432
433 inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
434 drop_nlink(inode);
435 dput(dentry);
436 return 0;
437}
438EXPORT_SYMBOL(simple_unlink);
439
440int simple_rmdir(struct inode *dir, struct dentry *dentry)
441{
442 if (!simple_empty(dentry))
443 return -ENOTEMPTY;
444
445 drop_nlink(d_inode(dentry));
446 simple_unlink(dir, dentry);
447 drop_nlink(dir);
448 return 0;
449}
450EXPORT_SYMBOL(simple_rmdir);
451
452int simple_rename_exchange(struct inode *old_dir, struct dentry *old_dentry,
453 struct inode *new_dir, struct dentry *new_dentry)
454{
455 bool old_is_dir = d_is_dir(old_dentry);
456 bool new_is_dir = d_is_dir(new_dentry);
457
458 if (old_dir != new_dir && old_is_dir != new_is_dir) {
459 if (old_is_dir) {
460 drop_nlink(old_dir);
461 inc_nlink(new_dir);
462 } else {
463 drop_nlink(new_dir);
464 inc_nlink(old_dir);
465 }
466 }
467 old_dir->i_ctime = old_dir->i_mtime =
468 new_dir->i_ctime = new_dir->i_mtime =
469 d_inode(old_dentry)->i_ctime =
470 d_inode(new_dentry)->i_ctime = current_time(old_dir);
471
472 return 0;
473}
474EXPORT_SYMBOL_GPL(simple_rename_exchange);
475
476int simple_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
477 struct dentry *old_dentry, struct inode *new_dir,
478 struct dentry *new_dentry, unsigned int flags)
479{
480 struct inode *inode = d_inode(old_dentry);
481 int they_are_dirs = d_is_dir(old_dentry);
482
483 if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
484 return -EINVAL;
485
486 if (flags & RENAME_EXCHANGE)
487 return simple_rename_exchange(old_dir, old_dentry, new_dir, new_dentry);
488
489 if (!simple_empty(new_dentry))
490 return -ENOTEMPTY;
491
492 if (d_really_is_positive(new_dentry)) {
493 simple_unlink(new_dir, new_dentry);
494 if (they_are_dirs) {
495 drop_nlink(d_inode(new_dentry));
496 drop_nlink(old_dir);
497 }
498 } else if (they_are_dirs) {
499 drop_nlink(old_dir);
500 inc_nlink(new_dir);
501 }
502
503 old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime =
504 new_dir->i_mtime = inode->i_ctime = current_time(old_dir);
505
506 return 0;
507}
508EXPORT_SYMBOL(simple_rename);
509
510/**
511 * simple_setattr - setattr for simple filesystem
512 * @mnt_userns: user namespace of the target mount
513 * @dentry: dentry
514 * @iattr: iattr structure
515 *
516 * Returns 0 on success, -error on failure.
517 *
518 * simple_setattr is a simple ->setattr implementation without a proper
519 * implementation of size changes.
520 *
521 * It can either be used for in-memory filesystems or special files
522 * on simple regular filesystems. Anything that needs to change on-disk
523 * or wire state on size changes needs its own setattr method.
524 */
525int simple_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
526 struct iattr *iattr)
527{
528 struct inode *inode = d_inode(dentry);
529 int error;
530
531 error = setattr_prepare(mnt_userns, dentry, iattr);
532 if (error)
533 return error;
534
535 if (iattr->ia_valid & ATTR_SIZE)
536 truncate_setsize(inode, iattr->ia_size);
537 setattr_copy(mnt_userns, inode, iattr);
538 mark_inode_dirty(inode);
539 return 0;
540}
541EXPORT_SYMBOL(simple_setattr);
542
543static int simple_read_folio(struct file *file, struct folio *folio)
544{
545 folio_zero_range(folio, 0, folio_size(folio));
546 flush_dcache_folio(folio);
547 folio_mark_uptodate(folio);
548 folio_unlock(folio);
549 return 0;
550}
551
552int simple_write_begin(struct file *file, struct address_space *mapping,
553 loff_t pos, unsigned len,
554 struct page **pagep, void **fsdata)
555{
556 struct page *page;
557 pgoff_t index;
558
559 index = pos >> PAGE_SHIFT;
560
561 page = grab_cache_page_write_begin(mapping, index);
562 if (!page)
563 return -ENOMEM;
564
565 *pagep = page;
566
567 if (!PageUptodate(page) && (len != PAGE_SIZE)) {
568 unsigned from = pos & (PAGE_SIZE - 1);
569
570 zero_user_segments(page, 0, from, from + len, PAGE_SIZE);
571 }
572 return 0;
573}
574EXPORT_SYMBOL(simple_write_begin);
575
576/**
577 * simple_write_end - .write_end helper for non-block-device FSes
578 * @file: See .write_end of address_space_operations
579 * @mapping: "
580 * @pos: "
581 * @len: "
582 * @copied: "
583 * @page: "
584 * @fsdata: "
585 *
586 * simple_write_end does the minimum needed for updating a page after writing is
587 * done. It has the same API signature as the .write_end of
588 * address_space_operations vector. So it can just be set onto .write_end for
589 * FSes that don't need any other processing. i_mutex is assumed to be held.
590 * Block based filesystems should use generic_write_end().
591 * NOTE: Even though i_size might get updated by this function, mark_inode_dirty
592 * is not called, so a filesystem that actually does store data in .write_inode
593 * should extend on what's done here with a call to mark_inode_dirty() in the
594 * case that i_size has changed.
595 *
596 * Use *ONLY* with simple_read_folio()
597 */
598static int simple_write_end(struct file *file, struct address_space *mapping,
599 loff_t pos, unsigned len, unsigned copied,
600 struct page *page, void *fsdata)
601{
602 struct inode *inode = page->mapping->host;
603 loff_t last_pos = pos + copied;
604
605 /* zero the stale part of the page if we did a short copy */
606 if (!PageUptodate(page)) {
607 if (copied < len) {
608 unsigned from = pos & (PAGE_SIZE - 1);
609
610 zero_user(page, from + copied, len - copied);
611 }
612 SetPageUptodate(page);
613 }
614 /*
615 * No need to use i_size_read() here, the i_size
616 * cannot change under us because we hold the i_mutex.
617 */
618 if (last_pos > inode->i_size)
619 i_size_write(inode, last_pos);
620
621 set_page_dirty(page);
622 unlock_page(page);
623 put_page(page);
624
625 return copied;
626}
627
628/*
629 * Provides ramfs-style behavior: data in the pagecache, but no writeback.
630 */
631const struct address_space_operations ram_aops = {
632 .read_folio = simple_read_folio,
633 .write_begin = simple_write_begin,
634 .write_end = simple_write_end,
635 .dirty_folio = noop_dirty_folio,
636};
637EXPORT_SYMBOL(ram_aops);
638
639/*
640 * the inodes created here are not hashed. If you use iunique to generate
641 * unique inode values later for this filesystem, then you must take care
642 * to pass it an appropriate max_reserved value to avoid collisions.
643 */
644int simple_fill_super(struct super_block *s, unsigned long magic,
645 const struct tree_descr *files)
646{
647 struct inode *inode;
648 struct dentry *root;
649 struct dentry *dentry;
650 int i;
651
652 s->s_blocksize = PAGE_SIZE;
653 s->s_blocksize_bits = PAGE_SHIFT;
654 s->s_magic = magic;
655 s->s_op = &simple_super_operations;
656 s->s_time_gran = 1;
657
658 inode = new_inode(s);
659 if (!inode)
660 return -ENOMEM;
661 /*
662 * because the root inode is 1, the files array must not contain an
663 * entry at index 1
664 */
665 inode->i_ino = 1;
666 inode->i_mode = S_IFDIR | 0755;
667 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
668 inode->i_op = &simple_dir_inode_operations;
669 inode->i_fop = &simple_dir_operations;
670 set_nlink(inode, 2);
671 root = d_make_root(inode);
672 if (!root)
673 return -ENOMEM;
674 for (i = 0; !files->name || files->name[0]; i++, files++) {
675 if (!files->name)
676 continue;
677
678 /* warn if it tries to conflict with the root inode */
679 if (unlikely(i == 1))
680 printk(KERN_WARNING "%s: %s passed in a files array"
681 "with an index of 1!\n", __func__,
682 s->s_type->name);
683
684 dentry = d_alloc_name(root, files->name);
685 if (!dentry)
686 goto out;
687 inode = new_inode(s);
688 if (!inode) {
689 dput(dentry);
690 goto out;
691 }
692 inode->i_mode = S_IFREG | files->mode;
693 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
694 inode->i_fop = files->ops;
695 inode->i_ino = i;
696 d_add(dentry, inode);
697 }
698 s->s_root = root;
699 return 0;
700out:
701 d_genocide(root);
702 shrink_dcache_parent(root);
703 dput(root);
704 return -ENOMEM;
705}
706EXPORT_SYMBOL(simple_fill_super);
707
708static DEFINE_SPINLOCK(pin_fs_lock);
709
710int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count)
711{
712 struct vfsmount *mnt = NULL;
713 spin_lock(&pin_fs_lock);
714 if (unlikely(!*mount)) {
715 spin_unlock(&pin_fs_lock);
716 mnt = vfs_kern_mount(type, SB_KERNMOUNT, type->name, NULL);
717 if (IS_ERR(mnt))
718 return PTR_ERR(mnt);
719 spin_lock(&pin_fs_lock);
720 if (!*mount)
721 *mount = mnt;
722 }
723 mntget(*mount);
724 ++*count;
725 spin_unlock(&pin_fs_lock);
726 mntput(mnt);
727 return 0;
728}
729EXPORT_SYMBOL(simple_pin_fs);
730
731void simple_release_fs(struct vfsmount **mount, int *count)
732{
733 struct vfsmount *mnt;
734 spin_lock(&pin_fs_lock);
735 mnt = *mount;
736 if (!--*count)
737 *mount = NULL;
738 spin_unlock(&pin_fs_lock);
739 mntput(mnt);
740}
741EXPORT_SYMBOL(simple_release_fs);
742
743/**
744 * simple_read_from_buffer - copy data from the buffer to user space
745 * @to: the user space buffer to read to
746 * @count: the maximum number of bytes to read
747 * @ppos: the current position in the buffer
748 * @from: the buffer to read from
749 * @available: the size of the buffer
750 *
751 * The simple_read_from_buffer() function reads up to @count bytes from the
752 * buffer @from at offset @ppos into the user space address starting at @to.
753 *
754 * On success, the number of bytes read is returned and the offset @ppos is
755 * advanced by this number, or negative value is returned on error.
756 **/
757ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
758 const void *from, size_t available)
759{
760 loff_t pos = *ppos;
761 size_t ret;
762
763 if (pos < 0)
764 return -EINVAL;
765 if (pos >= available || !count)
766 return 0;
767 if (count > available - pos)
768 count = available - pos;
769 ret = copy_to_user(to, from + pos, count);
770 if (ret == count)
771 return -EFAULT;
772 count -= ret;
773 *ppos = pos + count;
774 return count;
775}
776EXPORT_SYMBOL(simple_read_from_buffer);
777
778/**
779 * simple_write_to_buffer - copy data from user space to the buffer
780 * @to: the buffer to write to
781 * @available: the size of the buffer
782 * @ppos: the current position in the buffer
783 * @from: the user space buffer to read from
784 * @count: the maximum number of bytes to read
785 *
786 * The simple_write_to_buffer() function reads up to @count bytes from the user
787 * space address starting at @from into the buffer @to at offset @ppos.
788 *
789 * On success, the number of bytes written is returned and the offset @ppos is
790 * advanced by this number, or negative value is returned on error.
791 **/
792ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
793 const void __user *from, size_t count)
794{
795 loff_t pos = *ppos;
796 size_t res;
797
798 if (pos < 0)
799 return -EINVAL;
800 if (pos >= available || !count)
801 return 0;
802 if (count > available - pos)
803 count = available - pos;
804 res = copy_from_user(to + pos, from, count);
805 if (res == count)
806 return -EFAULT;
807 count -= res;
808 *ppos = pos + count;
809 return count;
810}
811EXPORT_SYMBOL(simple_write_to_buffer);
812
813/**
814 * memory_read_from_buffer - copy data from the buffer
815 * @to: the kernel space buffer to read to
816 * @count: the maximum number of bytes to read
817 * @ppos: the current position in the buffer
818 * @from: the buffer to read from
819 * @available: the size of the buffer
820 *
821 * The memory_read_from_buffer() function reads up to @count bytes from the
822 * buffer @from at offset @ppos into the kernel space address starting at @to.
823 *
824 * On success, the number of bytes read is returned and the offset @ppos is
825 * advanced by this number, or negative value is returned on error.
826 **/
827ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
828 const void *from, size_t available)
829{
830 loff_t pos = *ppos;
831
832 if (pos < 0)
833 return -EINVAL;
834 if (pos >= available)
835 return 0;
836 if (count > available - pos)
837 count = available - pos;
838 memcpy(to, from + pos, count);
839 *ppos = pos + count;
840
841 return count;
842}
843EXPORT_SYMBOL(memory_read_from_buffer);
844
845/*
846 * Transaction based IO.
847 * The file expects a single write which triggers the transaction, and then
848 * possibly a read which collects the result - which is stored in a
849 * file-local buffer.
850 */
851
852void simple_transaction_set(struct file *file, size_t n)
853{
854 struct simple_transaction_argresp *ar = file->private_data;
855
856 BUG_ON(n > SIMPLE_TRANSACTION_LIMIT);
857
858 /*
859 * The barrier ensures that ar->size will really remain zero until
860 * ar->data is ready for reading.
861 */
862 smp_mb();
863 ar->size = n;
864}
865EXPORT_SYMBOL(simple_transaction_set);
866
867char *simple_transaction_get(struct file *file, const char __user *buf, size_t size)
868{
869 struct simple_transaction_argresp *ar;
870 static DEFINE_SPINLOCK(simple_transaction_lock);
871
872 if (size > SIMPLE_TRANSACTION_LIMIT - 1)
873 return ERR_PTR(-EFBIG);
874
875 ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL);
876 if (!ar)
877 return ERR_PTR(-ENOMEM);
878
879 spin_lock(&simple_transaction_lock);
880
881 /* only one write allowed per open */
882 if (file->private_data) {
883 spin_unlock(&simple_transaction_lock);
884 free_page((unsigned long)ar);
885 return ERR_PTR(-EBUSY);
886 }
887
888 file->private_data = ar;
889
890 spin_unlock(&simple_transaction_lock);
891
892 if (copy_from_user(ar->data, buf, size))
893 return ERR_PTR(-EFAULT);
894
895 return ar->data;
896}
897EXPORT_SYMBOL(simple_transaction_get);
898
899ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos)
900{
901 struct simple_transaction_argresp *ar = file->private_data;
902
903 if (!ar)
904 return 0;
905 return simple_read_from_buffer(buf, size, pos, ar->data, ar->size);
906}
907EXPORT_SYMBOL(simple_transaction_read);
908
909int simple_transaction_release(struct inode *inode, struct file *file)
910{
911 free_page((unsigned long)file->private_data);
912 return 0;
913}
914EXPORT_SYMBOL(simple_transaction_release);
915
916/* Simple attribute files */
917
918struct simple_attr {
919 int (*get)(void *, u64 *);
920 int (*set)(void *, u64);
921 char get_buf[24]; /* enough to store a u64 and "\n\0" */
922 char set_buf[24];
923 void *data;
924 const char *fmt; /* format for read operation */
925 struct mutex mutex; /* protects access to these buffers */
926};
927
928/* simple_attr_open is called by an actual attribute open file operation
929 * to set the attribute specific access operations. */
930int simple_attr_open(struct inode *inode, struct file *file,
931 int (*get)(void *, u64 *), int (*set)(void *, u64),
932 const char *fmt)
933{
934 struct simple_attr *attr;
935
936 attr = kzalloc(sizeof(*attr), GFP_KERNEL);
937 if (!attr)
938 return -ENOMEM;
939
940 attr->get = get;
941 attr->set = set;
942 attr->data = inode->i_private;
943 attr->fmt = fmt;
944 mutex_init(&attr->mutex);
945
946 file->private_data = attr;
947
948 return nonseekable_open(inode, file);
949}
950EXPORT_SYMBOL_GPL(simple_attr_open);
951
952int simple_attr_release(struct inode *inode, struct file *file)
953{
954 kfree(file->private_data);
955 return 0;
956}
957EXPORT_SYMBOL_GPL(simple_attr_release); /* GPL-only? This? Really? */
958
959/* read from the buffer that is filled with the get function */
960ssize_t simple_attr_read(struct file *file, char __user *buf,
961 size_t len, loff_t *ppos)
962{
963 struct simple_attr *attr;
964 size_t size;
965 ssize_t ret;
966
967 attr = file->private_data;
968
969 if (!attr->get)
970 return -EACCES;
971
972 ret = mutex_lock_interruptible(&attr->mutex);
973 if (ret)
974 return ret;
975
976 if (*ppos && attr->get_buf[0]) {
977 /* continued read */
978 size = strlen(attr->get_buf);
979 } else {
980 /* first read */
981 u64 val;
982 ret = attr->get(attr->data, &val);
983 if (ret)
984 goto out;
985
986 size = scnprintf(attr->get_buf, sizeof(attr->get_buf),
987 attr->fmt, (unsigned long long)val);
988 }
989
990 ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
991out:
992 mutex_unlock(&attr->mutex);
993 return ret;
994}
995EXPORT_SYMBOL_GPL(simple_attr_read);
996
997/* interpret the buffer as a number to call the set function with */
998static ssize_t simple_attr_write_xsigned(struct file *file, const char __user *buf,
999 size_t len, loff_t *ppos, bool is_signed)
1000{
1001 struct simple_attr *attr;
1002 unsigned long long val;
1003 size_t size;
1004 ssize_t ret;
1005
1006 attr = file->private_data;
1007 if (!attr->set)
1008 return -EACCES;
1009
1010 ret = mutex_lock_interruptible(&attr->mutex);
1011 if (ret)
1012 return ret;
1013
1014 ret = -EFAULT;
1015 size = min(sizeof(attr->set_buf) - 1, len);
1016 if (copy_from_user(attr->set_buf, buf, size))
1017 goto out;
1018
1019 attr->set_buf[size] = '\0';
1020 if (is_signed)
1021 ret = kstrtoll(attr->set_buf, 0, &val);
1022 else
1023 ret = kstrtoull(attr->set_buf, 0, &val);
1024 if (ret)
1025 goto out;
1026 ret = attr->set(attr->data, val);
1027 if (ret == 0)
1028 ret = len; /* on success, claim we got the whole input */
1029out:
1030 mutex_unlock(&attr->mutex);
1031 return ret;
1032}
1033
1034ssize_t simple_attr_write(struct file *file, const char __user *buf,
1035 size_t len, loff_t *ppos)
1036{
1037 return simple_attr_write_xsigned(file, buf, len, ppos, false);
1038}
1039EXPORT_SYMBOL_GPL(simple_attr_write);
1040
1041ssize_t simple_attr_write_signed(struct file *file, const char __user *buf,
1042 size_t len, loff_t *ppos)
1043{
1044 return simple_attr_write_xsigned(file, buf, len, ppos, true);
1045}
1046EXPORT_SYMBOL_GPL(simple_attr_write_signed);
1047
1048/**
1049 * generic_fh_to_dentry - generic helper for the fh_to_dentry export operation
1050 * @sb: filesystem to do the file handle conversion on
1051 * @fid: file handle to convert
1052 * @fh_len: length of the file handle in bytes
1053 * @fh_type: type of file handle
1054 * @get_inode: filesystem callback to retrieve inode
1055 *
1056 * This function decodes @fid as long as it has one of the well-known
1057 * Linux filehandle types and calls @get_inode on it to retrieve the
1058 * inode for the object specified in the file handle.
1059 */
1060struct dentry *generic_fh_to_dentry(struct super_block *sb, struct fid *fid,
1061 int fh_len, int fh_type, struct inode *(*get_inode)
1062 (struct super_block *sb, u64 ino, u32 gen))
1063{
1064 struct inode *inode = NULL;
1065
1066 if (fh_len < 2)
1067 return NULL;
1068
1069 switch (fh_type) {
1070 case FILEID_INO32_GEN:
1071 case FILEID_INO32_GEN_PARENT:
1072 inode = get_inode(sb, fid->i32.ino, fid->i32.gen);
1073 break;
1074 }
1075
1076 return d_obtain_alias(inode);
1077}
1078EXPORT_SYMBOL_GPL(generic_fh_to_dentry);
1079
1080/**
1081 * generic_fh_to_parent - generic helper for the fh_to_parent export operation
1082 * @sb: filesystem to do the file handle conversion on
1083 * @fid: file handle to convert
1084 * @fh_len: length of the file handle in bytes
1085 * @fh_type: type of file handle
1086 * @get_inode: filesystem callback to retrieve inode
1087 *
1088 * This function decodes @fid as long as it has one of the well-known
1089 * Linux filehandle types and calls @get_inode on it to retrieve the
1090 * inode for the _parent_ object specified in the file handle if it
1091 * is specified in the file handle, or NULL otherwise.
1092 */
1093struct dentry *generic_fh_to_parent(struct super_block *sb, struct fid *fid,
1094 int fh_len, int fh_type, struct inode *(*get_inode)
1095 (struct super_block *sb, u64 ino, u32 gen))
1096{
1097 struct inode *inode = NULL;
1098
1099 if (fh_len <= 2)
1100 return NULL;
1101
1102 switch (fh_type) {
1103 case FILEID_INO32_GEN_PARENT:
1104 inode = get_inode(sb, fid->i32.parent_ino,
1105 (fh_len > 3 ? fid->i32.parent_gen : 0));
1106 break;
1107 }
1108
1109 return d_obtain_alias(inode);
1110}
1111EXPORT_SYMBOL_GPL(generic_fh_to_parent);
1112
1113/**
1114 * __generic_file_fsync - generic fsync implementation for simple filesystems
1115 *
1116 * @file: file to synchronize
1117 * @start: start offset in bytes
1118 * @end: end offset in bytes (inclusive)
1119 * @datasync: only synchronize essential metadata if true
1120 *
1121 * This is a generic implementation of the fsync method for simple
1122 * filesystems which track all non-inode metadata in the buffers list
1123 * hanging off the address_space structure.
1124 */
1125int __generic_file_fsync(struct file *file, loff_t start, loff_t end,
1126 int datasync)
1127{
1128 struct inode *inode = file->f_mapping->host;
1129 int err;
1130 int ret;
1131
1132 err = file_write_and_wait_range(file, start, end);
1133 if (err)
1134 return err;
1135
1136 inode_lock(inode);
1137 ret = sync_mapping_buffers(inode->i_mapping);
1138 if (!(inode->i_state & I_DIRTY_ALL))
1139 goto out;
1140 if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
1141 goto out;
1142
1143 err = sync_inode_metadata(inode, 1);
1144 if (ret == 0)
1145 ret = err;
1146
1147out:
1148 inode_unlock(inode);
1149 /* check and advance again to catch errors after syncing out buffers */
1150 err = file_check_and_advance_wb_err(file);
1151 if (ret == 0)
1152 ret = err;
1153 return ret;
1154}
1155EXPORT_SYMBOL(__generic_file_fsync);
1156
1157/**
1158 * generic_file_fsync - generic fsync implementation for simple filesystems
1159 * with flush
1160 * @file: file to synchronize
1161 * @start: start offset in bytes
1162 * @end: end offset in bytes (inclusive)
1163 * @datasync: only synchronize essential metadata if true
1164 *
1165 */
1166
1167int generic_file_fsync(struct file *file, loff_t start, loff_t end,
1168 int datasync)
1169{
1170 struct inode *inode = file->f_mapping->host;
1171 int err;
1172
1173 err = __generic_file_fsync(file, start, end, datasync);
1174 if (err)
1175 return err;
1176 return blkdev_issue_flush(inode->i_sb->s_bdev);
1177}
1178EXPORT_SYMBOL(generic_file_fsync);
1179
1180/**
1181 * generic_check_addressable - Check addressability of file system
1182 * @blocksize_bits: log of file system block size
1183 * @num_blocks: number of blocks in file system
1184 *
1185 * Determine whether a file system with @num_blocks blocks (and a
1186 * block size of 2**@blocksize_bits) is addressable by the sector_t
1187 * and page cache of the system. Return 0 if so and -EFBIG otherwise.
1188 */
1189int generic_check_addressable(unsigned blocksize_bits, u64 num_blocks)
1190{
1191 u64 last_fs_block = num_blocks - 1;
1192 u64 last_fs_page =
1193 last_fs_block >> (PAGE_SHIFT - blocksize_bits);
1194
1195 if (unlikely(num_blocks == 0))
1196 return 0;
1197
1198 if ((blocksize_bits < 9) || (blocksize_bits > PAGE_SHIFT))
1199 return -EINVAL;
1200
1201 if ((last_fs_block > (sector_t)(~0ULL) >> (blocksize_bits - 9)) ||
1202 (last_fs_page > (pgoff_t)(~0ULL))) {
1203 return -EFBIG;
1204 }
1205 return 0;
1206}
1207EXPORT_SYMBOL(generic_check_addressable);
1208
1209/*
1210 * No-op implementation of ->fsync for in-memory filesystems.
1211 */
1212int noop_fsync(struct file *file, loff_t start, loff_t end, int datasync)
1213{
1214 return 0;
1215}
1216EXPORT_SYMBOL(noop_fsync);
1217
1218ssize_t noop_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
1219{
1220 /*
1221 * iomap based filesystems support direct I/O without need for
1222 * this callback. However, it still needs to be set in
1223 * inode->a_ops so that open/fcntl know that direct I/O is
1224 * generally supported.
1225 */
1226 return -EINVAL;
1227}
1228EXPORT_SYMBOL_GPL(noop_direct_IO);
1229
1230/* Because kfree isn't assignment-compatible with void(void*) ;-/ */
1231void kfree_link(void *p)
1232{
1233 kfree(p);
1234}
1235EXPORT_SYMBOL(kfree_link);
1236
1237struct inode *alloc_anon_inode(struct super_block *s)
1238{
1239 static const struct address_space_operations anon_aops = {
1240 .dirty_folio = noop_dirty_folio,
1241 };
1242 struct inode *inode = new_inode_pseudo(s);
1243
1244 if (!inode)
1245 return ERR_PTR(-ENOMEM);
1246
1247 inode->i_ino = get_next_ino();
1248 inode->i_mapping->a_ops = &anon_aops;
1249
1250 /*
1251 * Mark the inode dirty from the very beginning,
1252 * that way it will never be moved to the dirty
1253 * list because mark_inode_dirty() will think
1254 * that it already _is_ on the dirty list.
1255 */
1256 inode->i_state = I_DIRTY;
1257 inode->i_mode = S_IRUSR | S_IWUSR;
1258 inode->i_uid = current_fsuid();
1259 inode->i_gid = current_fsgid();
1260 inode->i_flags |= S_PRIVATE;
1261 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
1262 return inode;
1263}
1264EXPORT_SYMBOL(alloc_anon_inode);
1265
1266/**
1267 * simple_nosetlease - generic helper for prohibiting leases
1268 * @filp: file pointer
1269 * @arg: type of lease to obtain
1270 * @flp: new lease supplied for insertion
1271 * @priv: private data for lm_setup operation
1272 *
1273 * Generic helper for filesystems that do not wish to allow leases to be set.
1274 * All arguments are ignored and it just returns -EINVAL.
1275 */
1276int
1277simple_nosetlease(struct file *filp, long arg, struct file_lock **flp,
1278 void **priv)
1279{
1280 return -EINVAL;
1281}
1282EXPORT_SYMBOL(simple_nosetlease);
1283
1284/**
1285 * simple_get_link - generic helper to get the target of "fast" symlinks
1286 * @dentry: not used here
1287 * @inode: the symlink inode
1288 * @done: not used here
1289 *
1290 * Generic helper for filesystems to use for symlink inodes where a pointer to
1291 * the symlink target is stored in ->i_link. NOTE: this isn't normally called,
1292 * since as an optimization the path lookup code uses any non-NULL ->i_link
1293 * directly, without calling ->get_link(). But ->get_link() still must be set,
1294 * to mark the inode_operations as being for a symlink.
1295 *
1296 * Return: the symlink target
1297 */
1298const char *simple_get_link(struct dentry *dentry, struct inode *inode,
1299 struct delayed_call *done)
1300{
1301 return inode->i_link;
1302}
1303EXPORT_SYMBOL(simple_get_link);
1304
1305const struct inode_operations simple_symlink_inode_operations = {
1306 .get_link = simple_get_link,
1307};
1308EXPORT_SYMBOL(simple_symlink_inode_operations);
1309
1310/*
1311 * Operations for a permanently empty directory.
1312 */
1313static struct dentry *empty_dir_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
1314{
1315 return ERR_PTR(-ENOENT);
1316}
1317
1318static int empty_dir_getattr(struct user_namespace *mnt_userns,
1319 const struct path *path, struct kstat *stat,
1320 u32 request_mask, unsigned int query_flags)
1321{
1322 struct inode *inode = d_inode(path->dentry);
1323 generic_fillattr(&init_user_ns, inode, stat);
1324 return 0;
1325}
1326
1327static int empty_dir_setattr(struct user_namespace *mnt_userns,
1328 struct dentry *dentry, struct iattr *attr)
1329{
1330 return -EPERM;
1331}
1332
1333static ssize_t empty_dir_listxattr(struct dentry *dentry, char *list, size_t size)
1334{
1335 return -EOPNOTSUPP;
1336}
1337
1338static const struct inode_operations empty_dir_inode_operations = {
1339 .lookup = empty_dir_lookup,
1340 .permission = generic_permission,
1341 .setattr = empty_dir_setattr,
1342 .getattr = empty_dir_getattr,
1343 .listxattr = empty_dir_listxattr,
1344};
1345
1346static loff_t empty_dir_llseek(struct file *file, loff_t offset, int whence)
1347{
1348 /* An empty directory has two entries . and .. at offsets 0 and 1 */
1349 return generic_file_llseek_size(file, offset, whence, 2, 2);
1350}
1351
1352static int empty_dir_readdir(struct file *file, struct dir_context *ctx)
1353{
1354 dir_emit_dots(file, ctx);
1355 return 0;
1356}
1357
1358static const struct file_operations empty_dir_operations = {
1359 .llseek = empty_dir_llseek,
1360 .read = generic_read_dir,
1361 .iterate_shared = empty_dir_readdir,
1362 .fsync = noop_fsync,
1363};
1364
1365
1366void make_empty_dir_inode(struct inode *inode)
1367{
1368 set_nlink(inode, 2);
1369 inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO;
1370 inode->i_uid = GLOBAL_ROOT_UID;
1371 inode->i_gid = GLOBAL_ROOT_GID;
1372 inode->i_rdev = 0;
1373 inode->i_size = 0;
1374 inode->i_blkbits = PAGE_SHIFT;
1375 inode->i_blocks = 0;
1376
1377 inode->i_op = &empty_dir_inode_operations;
1378 inode->i_opflags &= ~IOP_XATTR;
1379 inode->i_fop = &empty_dir_operations;
1380}
1381
1382bool is_empty_dir_inode(struct inode *inode)
1383{
1384 return (inode->i_fop == &empty_dir_operations) &&
1385 (inode->i_op == &empty_dir_inode_operations);
1386}
1387
1388#if IS_ENABLED(CONFIG_UNICODE)
1389/*
1390 * Determine if the name of a dentry should be casefolded.
1391 *
1392 * Return: if names will need casefolding
1393 */
1394static bool needs_casefold(const struct inode *dir)
1395{
1396 return IS_CASEFOLDED(dir) && dir->i_sb->s_encoding;
1397}
1398
1399/**
1400 * generic_ci_d_compare - generic d_compare implementation for casefolding filesystems
1401 * @dentry: dentry whose name we are checking against
1402 * @len: len of name of dentry
1403 * @str: str pointer to name of dentry
1404 * @name: Name to compare against
1405 *
1406 * Return: 0 if names match, 1 if mismatch, or -ERRNO
1407 */
1408static int generic_ci_d_compare(const struct dentry *dentry, unsigned int len,
1409 const char *str, const struct qstr *name)
1410{
1411 const struct dentry *parent = READ_ONCE(dentry->d_parent);
1412 const struct inode *dir = READ_ONCE(parent->d_inode);
1413 const struct super_block *sb = dentry->d_sb;
1414 const struct unicode_map *um = sb->s_encoding;
1415 struct qstr qstr = QSTR_INIT(str, len);
1416 char strbuf[DNAME_INLINE_LEN];
1417 int ret;
1418
1419 if (!dir || !needs_casefold(dir))
1420 goto fallback;
1421 /*
1422 * If the dentry name is stored in-line, then it may be concurrently
1423 * modified by a rename. If this happens, the VFS will eventually retry
1424 * the lookup, so it doesn't matter what ->d_compare() returns.
1425 * However, it's unsafe to call utf8_strncasecmp() with an unstable
1426 * string. Therefore, we have to copy the name into a temporary buffer.
1427 */
1428 if (len <= DNAME_INLINE_LEN - 1) {
1429 memcpy(strbuf, str, len);
1430 strbuf[len] = 0;
1431 qstr.name = strbuf;
1432 /* prevent compiler from optimizing out the temporary buffer */
1433 barrier();
1434 }
1435 ret = utf8_strncasecmp(um, name, &qstr);
1436 if (ret >= 0)
1437 return ret;
1438
1439 if (sb_has_strict_encoding(sb))
1440 return -EINVAL;
1441fallback:
1442 if (len != name->len)
1443 return 1;
1444 return !!memcmp(str, name->name, len);
1445}
1446
1447/**
1448 * generic_ci_d_hash - generic d_hash implementation for casefolding filesystems
1449 * @dentry: dentry of the parent directory
1450 * @str: qstr of name whose hash we should fill in
1451 *
1452 * Return: 0 if hash was successful or unchanged, and -EINVAL on error
1453 */
1454static int generic_ci_d_hash(const struct dentry *dentry, struct qstr *str)
1455{
1456 const struct inode *dir = READ_ONCE(dentry->d_inode);
1457 struct super_block *sb = dentry->d_sb;
1458 const struct unicode_map *um = sb->s_encoding;
1459 int ret = 0;
1460
1461 if (!dir || !needs_casefold(dir))
1462 return 0;
1463
1464 ret = utf8_casefold_hash(um, dentry, str);
1465 if (ret < 0 && sb_has_strict_encoding(sb))
1466 return -EINVAL;
1467 return 0;
1468}
1469
1470static const struct dentry_operations generic_ci_dentry_ops = {
1471 .d_hash = generic_ci_d_hash,
1472 .d_compare = generic_ci_d_compare,
1473};
1474#endif
1475
1476#ifdef CONFIG_FS_ENCRYPTION
1477static const struct dentry_operations generic_encrypted_dentry_ops = {
1478 .d_revalidate = fscrypt_d_revalidate,
1479};
1480#endif
1481
1482#if defined(CONFIG_FS_ENCRYPTION) && IS_ENABLED(CONFIG_UNICODE)
1483static const struct dentry_operations generic_encrypted_ci_dentry_ops = {
1484 .d_hash = generic_ci_d_hash,
1485 .d_compare = generic_ci_d_compare,
1486 .d_revalidate = fscrypt_d_revalidate,
1487};
1488#endif
1489
1490/**
1491 * generic_set_encrypted_ci_d_ops - helper for setting d_ops for given dentry
1492 * @dentry: dentry to set ops on
1493 *
1494 * Casefolded directories need d_hash and d_compare set, so that the dentries
1495 * contained in them are handled case-insensitively. Note that these operations
1496 * are needed on the parent directory rather than on the dentries in it, and
1497 * while the casefolding flag can be toggled on and off on an empty directory,
1498 * dentry_operations can't be changed later. As a result, if the filesystem has
1499 * casefolding support enabled at all, we have to give all dentries the
1500 * casefolding operations even if their inode doesn't have the casefolding flag
1501 * currently (and thus the casefolding ops would be no-ops for now).
1502 *
1503 * Encryption works differently in that the only dentry operation it needs is
1504 * d_revalidate, which it only needs on dentries that have the no-key name flag.
1505 * The no-key flag can't be set "later", so we don't have to worry about that.
1506 *
1507 * Finally, to maximize compatibility with overlayfs (which isn't compatible
1508 * with certain dentry operations) and to avoid taking an unnecessary
1509 * performance hit, we use custom dentry_operations for each possible
1510 * combination rather than always installing all operations.
1511 */
1512void generic_set_encrypted_ci_d_ops(struct dentry *dentry)
1513{
1514#ifdef CONFIG_FS_ENCRYPTION
1515 bool needs_encrypt_ops = dentry->d_flags & DCACHE_NOKEY_NAME;
1516#endif
1517#if IS_ENABLED(CONFIG_UNICODE)
1518 bool needs_ci_ops = dentry->d_sb->s_encoding;
1519#endif
1520#if defined(CONFIG_FS_ENCRYPTION) && IS_ENABLED(CONFIG_UNICODE)
1521 if (needs_encrypt_ops && needs_ci_ops) {
1522 d_set_d_op(dentry, &generic_encrypted_ci_dentry_ops);
1523 return;
1524 }
1525#endif
1526#ifdef CONFIG_FS_ENCRYPTION
1527 if (needs_encrypt_ops) {
1528 d_set_d_op(dentry, &generic_encrypted_dentry_ops);
1529 return;
1530 }
1531#endif
1532#if IS_ENABLED(CONFIG_UNICODE)
1533 if (needs_ci_ops) {
1534 d_set_d_op(dentry, &generic_ci_dentry_ops);
1535 return;
1536 }
1537#endif
1538}
1539EXPORT_SYMBOL(generic_set_encrypted_ci_d_ops);
1540
1541/**
1542 * inode_maybe_inc_iversion - increments i_version
1543 * @inode: inode with the i_version that should be updated
1544 * @force: increment the counter even if it's not necessary?
1545 *
1546 * Every time the inode is modified, the i_version field must be seen to have
1547 * changed by any observer.
1548 *
1549 * If "force" is set or the QUERIED flag is set, then ensure that we increment
1550 * the value, and clear the queried flag.
1551 *
1552 * In the common case where neither is set, then we can return "false" without
1553 * updating i_version.
1554 *
1555 * If this function returns false, and no other metadata has changed, then we
1556 * can avoid logging the metadata.
1557 */
1558bool inode_maybe_inc_iversion(struct inode *inode, bool force)
1559{
1560 u64 cur, new;
1561
1562 /*
1563 * The i_version field is not strictly ordered with any other inode
1564 * information, but the legacy inode_inc_iversion code used a spinlock
1565 * to serialize increments.
1566 *
1567 * Here, we add full memory barriers to ensure that any de-facto
1568 * ordering with other info is preserved.
1569 *
1570 * This barrier pairs with the barrier in inode_query_iversion()
1571 */
1572 smp_mb();
1573 cur = inode_peek_iversion_raw(inode);
1574 do {
1575 /* If flag is clear then we needn't do anything */
1576 if (!force && !(cur & I_VERSION_QUERIED))
1577 return false;
1578
1579 /* Since lowest bit is flag, add 2 to avoid it */
1580 new = (cur & ~I_VERSION_QUERIED) + I_VERSION_INCREMENT;
1581 } while (!atomic64_try_cmpxchg(&inode->i_version, &cur, new));
1582 return true;
1583}
1584EXPORT_SYMBOL(inode_maybe_inc_iversion);